Nitro and Azo Dyes 99 



Unfortunately just at the time when its value was most ap- 

 preciated it went off the market entirely because of the war. It 

 was not till after the close of the war that American manufacturers 

 learned its formula and discovered how to make it. 



A spectral curve of this dye is given in graph 3, Fig. 9, p. 86. 

 Characteristic of a black dye is the fact that there is considerable 

 light absorption even at the curve's minimum. 



D82 



(An acid dye) 



Occasional reference has been made to an orange S in the biologi- 

 cal literature, which we are informed by the dye industry is prob- 

 ably of the above composition. It was proposed by DeGalantha 

 (1936) in a mixture with alum hematoxylin for staining connective 

 tissue and following Harris' hematoxylin for demonstrating 

 amyloid. 



d85 victoria GREEI^ G 



A new trisazo dye of unknown chemical composition studied by 

 Cannon (1941) in connection with other new azo dyes. He states 

 it to have valuable properties as a nuclear stain in general histology. 



Other azo dyes sometimes mentioned in connection with hist- 

 ology are: 



Janus red; C. I. No. 266. 

 Tropaeolin O; C.I. No. 148. Syn: Chrysoin. Gold yellow. Acme 



yellow. 



Tropaeolin Y; C. I. No. 148 (see note). 



Roccellin; C. I. No. 176. Syn: Fast red A, AV, AL, BX, S or 0. 

 Cerasin. Rubidin. Cardinal red. 



Crystal ponceau 6R; C. I. No. 89; S>ti: Ponceau 6R. 



Carmine naphtha; C. I. No. 23. Syn: Sudan G. Oil yellow. 



Alizarin yellow GG; C. I. No. 36. Syn: Anthracene yellow GG, 

 Mordant yellow 2GT. 



Chlorazol paper brown B. A dye recently put out by the Im- 

 perial Chemical Industries of Manchester, England. Proposed 

 by Verdcourt (1947) for staining plant tissues. 



Chrysoidin R; C. I. No. 21. '^ya: Cotton orange. Cerotin orange. 



